Field of the Invention
The present invention relates to an antifouling coating composition, an antifouling coating film, an antifouling substrate, and method for producing an antifouling substrate.
Description of the Related Art
In ships, offshore structures, fishing nets, and the like, antifouling coatings containing a triorganosilyl ester-containing copolymer having low toxicity and small environmental loads as compared to organotin-based antifouling coatings have been used because of adherence of various marine species on portions immersed in seawater. However, a coating film containing the triorganosilyl ester-containing copolymer has had a problem that although the coating film dissolves in seawater at a constant rate for a given period from the early stage of immersion, the hydrolysis rate of the coating film is gradually increased, and after a lapse of a long period of time, the hydrolysis rate is excessively increased, water resistance is deteriorated, and cracking and peeling occur.
As antifouling coating compositions directed at improving crack resistance, there have been proposed: an antifouling coating composition comprising a silyl polymer, a polymeric plasticizer containing an ethylenically unsaturated carboxylic acid ester copolymer having a Tg of −20° C. or less and a number average molecular weight of 500 to 20,000, and an antifoulant (Patent Literature 1); an antifouling coating composition comprising a hydrolyzable silyl polymer, a polymer incompatible with the polymer, and a low-Tg polymer (Patent Literature 2); an antifouling coating composition comprising a trialkylsilyl polymer and a (meth)acrylate-based copolymer that is compatible with the polymer and has a number average molecular weight of 1,000 to 100,000 (Patent Literature 3); an antifouling coating composition comprising a trialkylsilyl polymer, a (meth)acrylate-based copolymer that is compatible with the polymer and has a number average molecular weight of 1,000 to 100,000, and chlorinated paraffin (Patent Literature 4); and the like.